Load release height control system for excavators

ABSTRACT

An excavator includes a dipper assembly configured to receive a dipper load, the dipper assembly having an actuated position for emptying the dipper load, a sensor assembly configured to monitor one or more operating conditions of the excavator, and a control module. The control module is configured to receive signals from the sensor assembly, determine a height of the dipper assembly relative to a surface, and inhibit movement of the dipper assembly to the actuated position.

TECHNICAL FIELD

This disclosure relates to excavators having a dipper or bucket, and particularly to a control system for controlling the movement of the dipper or bucket. The disclosure relates more particularly to a control system for controlling a height above a deposit point at which the excavator releases its load from the dipper.

BACKGROUND

This section is intended to provide a background or context to the invention recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.

Excavators, such as mining shovels, often include a shovel dipper or bucket for scooping earth and other materials. The shovel dipper may be formed with teeth at its leading edge and a dipper door that closes the rear of the dipper to hold the materials that are loaded into the dipper by the action of the mining shovel. The dipper door is typically held closed while the dipper is being loaded and while the load in the dipper is swung to a deposit point (e.g., haul truck, dumpster, etc.). At that point, the dipper door is opened to allow the contents of the dipper to empty.

Typically, a shovel operator controls the movement of the dipper, “tripping” (i.e., releasing) the dipper door once the dipper is above the deposit point, allowing the contents of the dipper (i.e., the “dipper load”) to empty into or onto the deposit point. In some instances, the impact from the falling dipper load may cause damage to the deposit point. For example, if the dipper load is emptied from an excessive height to a load transport vehicle (“haul truck”), the dipper load may deliver an excessive force upon impact, causing damage to one or more components of the haul truck, such as the truck bed, vehicle suspension, etc. The height at which the dipper load may be safely emptied depends on a number of factors, including the type of excavator, the type of deposit point, the weight of the dipper load, and the type of material comprising the dipper load. Most excavators are manually controlled by an operator who must determine an appropriate release height for each dipper load, which can lead to damage to the deposit point, excavator, or other surrounding equipment due to operator error or misjudgment.

Some excavators may include swing automation intended to restrict the motion of the dipper or bucket. An example of such swing automation can be found in U.S. Patent Publication No. 2012/0263566, published Oct. 18, 2012, for “Swing Automation for Rope Shovel,” which discloses a controller which monitors the hoist and crowd position of the dipper, and prevents motion of the dipper “past a boundary limit of the ideal path.” However, the disclosed controller prevents movement of the dipper outside of an ideal swing path, which may restrict the excavator from efficiently performing certain necessary or useful operations. The disclosed controller also includes only a single ideal path for the dipper, rather than accounting for the weight of the dipper load, the height of the deposit point, or any other factors or conditions related to the operation of the excavator, or location of the haul truck, etc.

SUMMARY

An embodiment of the present disclosure relates to an excavator. The excavator includes a dipper assembly configured to receive a dipper load, the dipper assembly having an actuated position for emptying the dipper load, a sensor assembly configured to monitor one or more operating conditions of the excavator, and a control module. The control module is configured to receive signals from the sensor assembly, determine a height of the dipper assembly relative to a surface, and inhibit movement of the dipper assembly to the actuated position.

Another embodiment of the present disclosure relates to a mining shovel. The mining shovel includes a dipper configured to receive a dipper load, the dipper having an open dipper bottom, a dipper door coupled to the dipper, the dipper door having a first position for covering the open dipper bottom and a second position for emptying the dipper load, a sensor assembly configured to monitor a height of the dipper relative to a surface, and a control module configured to receive signals from the sensor assembly, and to control the movement of the dipper door between the first and second positions.

Another embodiment of the present disclosure relates to a control system for a dipper assembly having an actuated position for emptying a dipper load. The control system includes a sensor assembly configured to monitor a height of the dipper assembly relative to a surface and monitor a weight of the dipper load, and a control module configured to receive signals from the sensor assembly, calculate a dipper height limit based on the signals, and inhibit movement of the dipper assembly to the actuated position when the dipper assembly is above the dipper height limit.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements, in which:

FIG. 1 is a side view of a mining shovel of the present disclosure, according to an exemplary embodiment.

FIG. 2 is a perspective view of a dipper assembly for the mining shovel of FIG. 1, according to an exemplary embodiment.

FIG. 3 is a side view of a dipper assembly for the mining shovel positioned above a haul truck, according to an exemplary embodiment.

FIG. 4 is a schematic representation of the load release height control system of the present disclosure, according to an exemplary embodiment.

FIG. 5 is a flow chart representation of the load release height control system of the present disclosure, according to an exemplary embodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.

Referring to FIGS. 1 and 2, a mining shovel 10 having a dipper 12 is shown, according to an exemplary embodiment. In this embodiment, the mining shovel 10 includes a dipper arm 20 coupled to a dipper 12 and supported by a boom assembly 22. The dipper 12 includes teeth forming a leading edge 14 for scooping earth and other material (e.g., rock, sand, etc.) and has an open dipper bottom 18 covered by a dipper door 16. The dipper 12 together with the dipper door 16 may form a dipper assembly. In other embodiments, the dipper assembly may include other parts or components as is suitable for the particular application of the mining shovel 10 and/or the load release height control system of the present disclosure. Material is loaded into the dipper 12 by the action of the mining shovel 10, and the dipper door 16 is configured to cover the open dipper bottom 18 to prevent the material (i.e., the dipper load) from emptying prematurely. In an exemplary embodiment, the dipper door 16 is movable between a closed position (shown in FIGS. 1 and 2) for covering the open dipper bottom 18, and an open position (i.e., actuated position) for emptying the contents of the dipper 12. The dipper door 16 is held in the closed position while the dipper 12 is being loaded and while the dipper load is swung to a deposit point such as haul truck 28 (shown in FIG. 3). The dipper door 16 is then released to the open position, emptying the dipper load at a height above the deposit point. In the illustrated embodiment of FIGS. 1-3, the mining shovel 10 includes trip ropes 32 coupled to the dipper door 16 and configured to release the dipper door 16, allowing the dipper door 16 to swing or move to the open position. In this embodiment, the trip ropes 32 may be controllable by an operator of the mining shovel 10, such that the operator is able to “trip” (i.e., release) the dipper door 16 (i.e., by manipulating a control panel or otherwise), allowing the dipper door 16 to swing or move to the open position and emptying the contents of the dipper 12.

Although the disclosure is shown and described by way of example with reference to mining shovel 10, the disclosure is also applicable for use with any digging machine having a dipper (e.g., dipper 12, etc.) or bucket for scooping and emptying loads of material, such as excavators, wheel loaders, etc., all of which are intended to be within the scope of this disclosure.

Referring now to FIG. 3, the dipper assembly is shown positioned above a deposit point shown as haul truck 28, according to an exemplary embodiment. In this embodiment, the haul truck 28 includes a truck bed 30 for receiving a dipper load. The mining shovel 10 is configured to scoop material into the dipper 12 in order to fill the dipper 12 with a dipper load, swing the dipper 12 to a height above the truck bed 30, and then rotate the dipper 12 such that the dipper bottom 18 is oriented to face the truck bed 30 (i.e., such that the closed dipper door 16 is on the bottom of the dipper 12, according to FIG. 3). Once the dipper 12 is properly oriented above the surface of the truck bed 30, the dipper door 16 may be released to reveal the open dipper bottom 18 and empty the dipper load into the truck bed 30.

Referring to FIG. 4, in an exemplary embodiment the mining shovel 10 includes a control system (i.e., load release height control system) that, among other control features, is intended to prevent or otherwise inhibit the mining shovel 10 from emptying the dipper load under conditions in which the impact of the dipper load may apply an excessive load force to the haul truck 28 (or another deposit point). For instance, an excessive load force may be applied to a deposit point such as haul truck 28 when the dipper contents are released from above a certain height relative to the deposit point or relative to a surface of the deposit point (hereinafter referred to as “the dipper height limit”). The dipper height limit may be calculated or determined based on a number of factors, including the weight of the dipper load, the type of material comprising the dipper load, the specific characteristics of the deposit point (e.g., haul truck 28, etc.) and/or the excavator (e.g., mining shovel 10, etc.), the type of surface underneath the deposit point and/or the excavator, or any other number factors or conditions related to the digging operation. In the illustrated embodiment of the FIGURES, the control system for the mining shovel 10 is configured to prevent the dipper 12 from emptying the dipper contents when the dipper 12 is above the dipper height limit, thus preventing damage to the haul truck 28. It should be noted that although the haul truck 28 is shown by way of example in FIG. 3 and referred to throughout, the disclosure is also applicable for use in conjunction with any other deposit point for receiving dipper loads, including dump trucks, dumpsters, conveyors, etc., all of which are intended to be within the scope of this disclosure.

In an exemplary embodiment, the control system includes a sensor assembly 36 for monitoring one or more factors or conditions related to the operations of the mining shovel 10 (i.e., operating conditions). The operating conditions of the mining shovel 10 (i.e., excavator) may include any factor or condition necessary or useful for determining the dipper height limit, including any condition related to the mining shovel 10, the deposit point, and/or the surrounding environment. For instance, the sensor assembly 36 may be configured to monitor a height of the dipper 12 or a dipper assembly relative to a surface (i.e., the deposit point) in order to determine whether the dipper 12 is above or below the dipper height limit. The sensor assembly 36 may also be configured to monitor a weight of the dipper load, the shape or position of the deposit point or another related machine or component, the weather conditions in the area surrounding the mining shovel 10, the condition of the ground or surface underneath the mining shovel 10 and/or the deposit point, or any other factor or condition necessary or useful for determining the dipper height limit.

The sensor assembly 36 may be configured to monitor the height of the dipper 12 relative to the deposit point in one or more ways, depending on the suitability for the particular application of the control system. For example, the sensor assembly 36 may be configured to directly measure the height of the dipper 12 relative to the deposit point by mounting one or more sensors to the dipper 12 and pointing the sensors in the direction of the deposit point. In other embodiments, the sensor assembly 36 may be configured to monitor the height of the dipper 12 relative to a base 40 of the mining shovel 10, relative to the boom assembly 22, relative to another component of the mining shovel 10, or relative to the ground, in order to calculate or estimate the distance between the dipper 12 and the deposit point. In still other embodiments, the sensor assembly 36 is configured to monitor or measure the distance between the dipper 12 and another marker or point in the surrounding area, such that the height of the dipper 12 relative to the deposit point can be calculated or estimated.

In some embodiments, the sensor assembly 36 is centrally located, having a single area in which the sensor assembly 36 is positioned and/or mounted. For instance, the sensor assembly 36 may be coupled to a single component of the mining shovel 10 (e.g., the dipper 12, the boom assembly 22, the dipper arm 20, etc.), or positioned in another location suitable for monitoring the relative height of the dipper 12 and/or one or more other conditions related to the mining shovel 10. In other embodiments, the sensor assembly 36 includes multiple elements having more than one location. For instance, in one embodiment the sensor assembly 36 includes one or more elements coupled to the dipper 12 (as shown in FIG. 1), one or more elements coupled to a deposit point such as haul truck 28, and one or more elements positioned in another location suitable for monitoring one or more conditions related to the mining shovel 10.

In some embodiments, the sensor assembly 36 includes one or more laser sensors (e.g., laser distance meters, laser rangefinders, etc.) configured to monitor the height of the dipper 12. The laser sensors may be mounted on the dipper 12 and configured to measure distances relative to the dipper 12. In an exemplary embodiment, the laser sensors are configured to send one or more laser pulses in the direction of the haul truck 28 in order to measure a distance between the dipper 12 and the haul truck 28, and thus determine a relative height of the dipper 12. In such an embodiment, the laser pulse is reflected by a surface of the haul truck 28 back in the direction of the laser sensors. The laser sensors are configured to determine the distance between the dipper 12 and the haul truck 28 (i.e., the relative height of the dipper 12) based on the time taken by the pulse to be reflected off of the truck bed 30 and returned to the laser sensors. The laser sensors may be positioned on the dipper 12 such that a laser pulse is sent in the direction of the truck bed 30 when the dipper 12 is in a dumping or emptying position (i.e., when the dipper door 16 is oriented at the bottom of the dipper 12 and facing the truck bed 30). Once the relative height of the dipper 12 is determined, the laser sensors (e.g., sensor assembly 36) are configured to send one or more signals to the control module 26 representing the time taken to reflect the laser pulse and/or representing the relative height of the dipper 12.

The sensor assembly 36 may also include one or more laser scanners for monitoring the area surrounding the dipper 12. The laser scanners are configured to emit one or more laser beams in order to build a three-dimensional surface map (i.e., three-dimensional map) of the surrounding area. The laser scanners may be rotatable, configured to rotate up to 360 degrees around a single point while emitting one or more laser beams, or the laser scanners may be stationary and include rotatable laser beams configured to rotate up to 360 degrees around the stationary laser scanner. In an exemplary embodiment, a laser scanner is mounted to the dipper 12. In this embodiment, the laser scanner emits one or more laser beams in all directions around the dipper 12, and the beams are reflected off of the surrounding surfaces (e.g., the ground, haul truck 28, other components of mining shovel 10, etc.), back to the laser scanner. The laser scanner may be configured to determine the distance between the dipper 12 and one or more surrounding surfaces based on the time taken by the laser beam to be reflected off of a surrounding surface and returned to the laser scanner. In one embodiment, the sensor assembly 36 uses the distances measured by the laser beams to build a three-dimensional surface map of the area surrounding the dipper 12, sending one or more signals representing the three-dimensional surface map to the control module 26. In another embodiment, the sensor assembly 36 sends one or more signals representing the distances measured by the laser beams to the control module 26, and the control module 26 is configured to build a three-dimensional surface map of the area surrounding the dipper 12 using the signals. The laser scanner may be configured to continuously emit laser beams so that the three-dimensional surface map is continuously updated. The control module 26 may use the three-dimensional surface map to determine a relative height of the dipper 12, a distance between the dipper 12 and a surrounding surface, or another distance or height measured by the laser scanner.

The sensor assembly 36 may also include one or more infrared sensors configured to monitor a relative height of the dipper 12. The infrared sensors may be positioned or coupled to the dipper 12 or another component of the mining shovel 10 and configured to point in the direction of a deposit point or another surface in order to measure the distance between the dipper 12 and the deposit point (i.e., the relative height of the dipper 12). The infrared sensors may then send one or more signals representing the relative height of the dipper 12 to the control module 26, and the control module 26 may utilize the signals to calculate or determine the dipper height limit.

The sensor assembly 36 may also include one or more vision sensors (e.g., cameras, video cameras, photosensors, etc.) configured to monitor a relative height of the dipper 12. In an exemplary embodiment, the vision sensors are coupled to the dipper 12 or to another component of the mining shovel 10. The vision sensors are configured to capture an image of the deposit point in order to monitor the distance between the dipper 12 and the deposit point. The vision sensors may be configured to send one or more signals to the control module 26 representing one or more measured distances. The vision sensors may also be configured to determine a distance between the dipper 12 and one or more components and/or surfaces. The sensor assembly 36 may also include one or more GPS sensors. The GPS sensors may be coupled to a component of the mining shovel 10, coupled to a component of the deposit point, or positioned in another location suitable for monitoring the distance between the dipper 12 and the deposit point. The GPS sensors may be configured to measure a distance between the dipper 12 and one or more components or surfaces, and to send one or more signals to the control module 26 representing the relative distance.

In one exemplary embodiment, the sensor assembly 36 may include one or more position sensors (e.g., proximity sensors, etc.) configured to monitor a relative height of the dipper 12. For instance, position sensors may be coupled to the dipper arm 20 or the boom assembly 22 in order to monitor the relative position of the dipper arm 20 or boom assembly 22, and configured to send one or more signals to the control module 26 representing the position of the dipper arm 20, the boom assembly 22, and/or the dipper 12. In an exemplary embodiment, the mining shovel 10 includes a hydraulic cylinder (not shown) for crowding the dipper 12. In this embodiment, a position sensor may be coupled to the hydraulic cylinder (i.e., crowd cylinder) and configured to monitor the relative position of the hydraulic cylinder. In some embodiments, the position sensor sends one or more signals to the control module 26 representing the relative position of the monitored component (e.g., dipper arm 20, boom assembly 22, hydraulic cylinder, etc.), and the control module 26 is configured to calculate the relative height of the dipper 12 from the signals. In other embodiments, the position sensor may calculate or determine the relative height of the dipper based on the relative position of the monitored component, and send one or more signals to the control module 26 representing the relative height of the dipper 12.

In some embodiments, the control module 26 is configured to calculate or determine the height of the dipper 12 relative to the deposit point without the use of the sensor assembly 36. For instance, the control module 26 may determine the height of the dipper relative to the deposit point based on the position of the boom assembly 22, the dipper arm 20, the cables 24, and/or another component of the mining shovel 10. The control module 26 may also be configured to determine the height of the dipper 12 relative to the deposit point based on information or signals received from the operator, such as through an operator interface 34 (e.g., wireless communication device, control panel, etc.). In other embodiments, the control module 26 is configured to calculate or determine the height of the dipper 12 relative to the deposit point in another manner suitable for the particular application of the load release height control system.

In some embodiments, the sensor assembly 36 may include weight sensors for monitoring the weight of the dipper load. The weight sensors may be configured to monitor a weight of the dipper load, and to send one or more signals to the control module 26 representing the weight of the dipper load. The control module 26 may be configured to use the signals from the weight sensors, as well as signals or information regarding other relevant conditions (e.g., type of material in the dipper load, type of deposit point, etc.), to calculate the dipper height limit above which the emptied dipper load may apply an excessive force to the deposit point. The weight sensors may be coupled to the dipper 12, coupled to the dipper arm 20, or mounted or positioned in another location on the mining shovel 10 suitable for monitoring the weight of the dipper load. In one embodiment, the weight sensors are connected to cables 24 which suspend the dipper arm 20 and dipper 12. In this embodiment, the weight sensors are configured to measure the tension in the cables 24 necessary to hold the dipper arm 20 and the dipper 12 in place. The weight sensors may be configured to determine the weight of the dipper load based on the measured tension in the cables 24. The weight sensors may also be configured to send one or more signals to the control module 26 representing the tension in the cables 24, and the control module 26 may be configured to calculate the weight of the dipper load from these signals.

In an exemplary embodiment, the control module 26 is configured to receive one or more signals from the sensor assembly 36, the signals representing one or more conditions of the mining shovel 10 and/or the deposit point (i.e., operating conditions). The control module 26 may also be configured to receive operator input from the operator interface 34. The control module 26 may be configured to use the signals and/or the operator input to calculate or determine the dipper height limit. For instance, the dipper height limit may be calculated based on some combination of the weight of the dipper load, the height of the dipper 12 relative to the deposit point, the type of material within the dipper 12, the ground surface underneath the mining shovel 10 and/or the deposit point, input received from the operator interface 34, or any other relevant factors or conditions measured by the sensor assembly 36 and/or the control module 26. In some embodiments, a predetermined dipper height limit may be manually entered into the control module 26 by an operator through the operator interface 34. The control module 26 may also be configured to receive one or more manually entered conditions or factors related to the mining shovel 10 from the operator interface 34, and to calculate or determine a dipper height limit based on these manually entered conditions.

The control module 26 may be configured to utilize the calculated or predetermined dipper height limit in order to prevent damage to the deposit point from a dipper load released from an excessive height (i.e., above the dipper height limit). In an exemplary embodiment, the control module 26 is configured to monitor the height of the dipper 12. In some embodiments, the control module 26 is configured to prevent the dipper door 16 from moving from the closed position to the open position (e.g., by actuating or applying an interlock, etc.) when the dipper 12 is above the dipper height limit, thus preventing the dipper 12 from emptying its contents from an excessive height.

In some embodiments, the control module 26 is configured to otherwise inhibit the movement of the dipper door 16 from the closed position to the open position when the dipper 12 is above the dipper height limit. For instance, in an exemplary embodiment the dipper assembly includes snubbers or brakes (not shown) coupled to the dipper door 16 and configured to slow the movement of the dipper door 16 from the closed position to the open position. In this embodiment, the control module 26 may be configured to control the movement and/or actuation of the snubbers or brakes in order to selectively slow the movement of the dipper door 16, reducing the amount of material from the dipper load that is released from the dipper 12 at any time, and thus reducing the force applied by the dipper load to the deposit point at any time.

When the dipper 12 is above the dipper height limit, the control module 26 may also be configured to provide one or more audible, visual, or other sensory indications or warnings (e.g., tactile/audible feedback, warning light, noise, alarm, haptic joystick, etc.) to the operator of the mining shovel 10, indicating that the dipper contents may cause damage to the deposit point if emptied.

In one exemplary embodiment, the control module 26 may be configured to automatically position the dipper 12 based on the signals received from the sensor assembly 36. For instance, if the dipper 12 is positioned above the dipper height limit and the operator attempts to move the dipper assembly to the actuated position (i.e., release the dipper door 16) to empty the contents of the dipper 12, the control module 26 may be configured to automatically lower the dipper 12 until the dipper 12 is positioned below the dipper height limit. The control module 26 may also be configured to instruct the operator to manually lower the dipper 12 by the necessary amount so that the dipper 12 is positioned below the dipper height limit before emptying the contents of the dipper 12.

Referring now to FIG. 5, a flow chart representation of the load release height control system is shown, according to an exemplary embodiment. In this embodiment, the control module 26 is configured to receive signals representing operating conditions of the mining shovel 10 (e.g., weight of the dipper load, height of the dipper 12, ground conditions, type of material in dipper load, deposit point conditions, weather conditions, etc.) from the sensor assembly 36, as well as operator input (e.g., dipper height limit, other operating conditions, etc.) from the operator interface 34 (e.g., wireless communication device, control panel, etc.). The sensor assembly 36 may include laser sensors, vision sensors, weight sensors, infrared sensors, GPS sensors, or other sensors or components configured to monitor one or more operating conditions of the mining shovel 10. In this embodiment, the control module 26 receives the signals and input, and determines whether the height of the dipper 12 relative to the deposit point (i.e., surface) is above the dipper height limit. If not, the control module 26 may allow the dipper 12 to actuate or move to the actuated position to empty the dipper load to the deposit point. If so, the control module 26 may create a response such as a warning for the operator, inhibit the movement of the dipper 12 to the actuated position, and/or automatically lower the height of the dipper 12 below the dipper height limit. The control module 26 may also be programmed to calculate the dipper height limit based on the signals from the sensor assembly 36 and the input from the operator interface 34.

The construction and arrangements of the load release height control system for excavators, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process, logical algorithm, or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.

INDUSTRIAL APPLICABILITY

The disclosed load release height control system for excavators may be implemented into any machine having a dipper or bucket for excavating material. The disclosed load release height control system for excavators may prevent damage to deposit points or surfaces such as haul trucks by preventing the excavator from applying an excessive force to the deposit point. The disclosed load release height control system may monitor the height of a dipper or bucket for an excavator, preventing the dipper from emptying its contents from above a dipper height limit, and thus preventing the contents of the dipper from applying an excessive force and damaging the deposit point.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed load release height control system for excavators. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed load release height control system for excavators. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents. 

What is claimed is:
 1. An excavator, comprising: a dipper assembly configured to receive a dipper load, the dipper assembly having an actuated position for emptying the dipper load; a sensor assembly configured to monitor one or more operating conditions of the excavator; and a control module configured to: receive signals from the sensor assembly; determine a height of the dipper assembly relative to a surface; and inhibit movement of the dipper assembly to the actuated position.
 2. The excavator of claim 1, wherein the control module is programmed to prevent movement of the dipper assembly to the actuated position when the height of the dipper assembly relative to the surface is greater than a dipper height limit.
 3. The excavator of claim 2, wherein the one or more operating conditions of the excavator comprise the height of the dipper assembly relative to the surface.
 4. The excavator of claim 3, wherein the control module is programmed to calculate the dipper height limit at least in part from the signals received from the sensor assembly.
 5. The excavator of claim 2, wherein the sensor assembly is configured to monitor a weight of the dipper load, and the control module is programmed to calculate the dipper height limit at least partly based on the weight of the dipper load.
 6. The excavator of claim 1, wherein the control module is programmed to calculate the height of the dipper assembly relative to the surface based at least in part on the signals received from the sensor assembly.
 7. The excavator of claim 2, wherein the control module is configured to provide a warning to an operator of the excavator when the height of the dipper assembly relative to the surface is greater than the dipper height limit.
 8. The excavator of claim 2, wherein the control module is configured to control the dipper assembly, the control module being programmed to automatically lower the height of the dipper assembly to a position below the dipper height limit before allowing the dipper assembly to move to the actuated position.
 9. The excavator of claim 1, wherein the sensor assembly comprises a laser sensor configured to measure a distance relative to the dipper assembly.
 10. The excavator of claim 1, wherein the sensor assembly comprises a laser scanner configured to build a three-dimensional map of an area surrounding the dipper assembly.
 11. The excavator of claim 1, wherein the sensor assembly comprises an infrared sensor configured to measure a distance relative to the dipper assembly.
 12. A mining shovel, comprising: a dipper configured to receive a dipper load, the dipper having an open dipper bottom; a dipper door coupled to the dipper, the dipper door having a first position for covering the open dipper bottom and a second position for emptying the dipper load; a sensor assembly configured to monitor a height of the dipper relative to a surface; and a control module configured to receive signals from the sensor assembly, and to control the movement of the dipper door between the first and second positions.
 13. The mining shovel of claim 12, wherein the control module is programmed to prevent movement of the dipper door from the first position to the second position when the height of the dipper relative to the surface is greater than a dipper height limit.
 14. The mining shovel of claim 13, wherein the sensor assembly is configured to monitor one or more operating conditions of the mining shovel.
 15. The mining shovel of claim 14, wherein the control module is programmed to calculate the dipper height limit at least in part from the signals received from the sensor assembly.
 16. The mining shovel of claim 13, wherein the control module is configured to slow movement of the dipper door from the first position to the second position when the height of the dipper relative to the surface is greater than the dipper height limit.
 17. The mining shovel of claim 13, wherein the control module is configured to control the dipper, the control module being programmed to automatically lower the height of the dipper to a position below the dipper height limit before allowing the dipper door to move to the second position.
 18. A control system for a dipper assembly having an actuated position for emptying a dipper load, the control system comprising: a sensor assembly configured to: monitor a height of the dipper assembly relative to a surface; and monitor a weight of the dipper load; a control module configured to: receive signals from the sensor assembly; calculate a dipper height limit based on the signals; and inhibit movement of the dipper assembly to the actuated position when the dipper assembly is above the dipper height limit.
 19. The control system of claim 18, wherein the control module is configured to create a response when the height of the dipper assembly relative to the surface is greater than the dipper height limit.
 20. The control system of claim 18, wherein the control module is configured to control the dipper assembly, the control module being programmed to automatically lower the height of the dipper assembly to a position below the dipper height limit before allowing the dipper assembly to move to the actuated position. 